The compressor of this kind includes a cylinder block in which plural cylinder bores are formed, a front housing assembled to the front side of the cylinder block to define a crank chamber, and a rear housing attached to the rear side of the cylinder block via a valve plate, in which a suction chamber and a discharge chamber are formed, in which pistons are arranged in respective cylinder bores of the cylinder block so as to reciprocate, a shaft is supported by the front housing and the cylinder block so as to rotate freely, a swash plate rotating integrally with the shaft so that a tilt angle with respect to the shaft is variable is provided in the shaft, and engaging portions of the pistons are engaged with a peripheral edge portion of the swash plate through shoes, thereby converting a rotary motion of the swash plate into a reciprocating motion of the pistons through the shoes.
Moreover, a supply passage for allowing the discharge chamber to communicate with the crank chamber and an release passage for allowing the crank chamber to communicate with the suction chamber are provided. The pressure inside the crank chamber is controlled by arranging a control valve in the supply passage and adjusting the amount of working fluid flowing from the discharge chamber to the crank chamber by the control value for example, thereby changing the tilt angle of the swash plate with respect to the shaft and controlling the discharge amount. As oil is mixed in a working fluid flowing through the supply passage, the oil is supplied to the crank chamber by supplying the working fluid to the crank chamber.
In this case, as fluids entering the crank chamber, there are a supply gas supplied from the discharge chamber and a blowby gas entering from clearances between the cylinder bores and the pistons. As a fluid going out from the crank chamber, there is an release gas going out into the suction chamber formed in the rear housing through the release passage. Therefore, the oil amount (amount of lubricating oil) inside the crank chamber may vary by the flow of these fluids according to operation conditions.
Incidentally, when the oil amount inside the crank chamber is too small, there is a danger of seizure occurring in a sliding portion such as the swash plate due to lubrication shortage. Accordingly, a device for giving a function of separating oil to the inside of the crank chamber and so on have been considered in the past for preventing the oil from being taken out from the crank chamber (for allowing the oil to be held in the crank chamber).
For example, in a piston compressor disclosed in Patent Literature 1 below, an release hole forming part of an release passage for releasing the working fluid flowing into the crank chamber to the suction chamber is formed in a shaft, and the release hole formed in the shaft is configured by an axial direction passage provided along a shaft center from a rear end of the shaft toward a front end side and a radial direction passage communicating with the axial direction passage and opening to the crank chamber to form an entrance portion of the release passage, thereby separating oil from the working fluid flowing from the radial direction passage by using a centrifugal force generated by rotation of the shaft.